Tool With Modular Pressure Compensator And Related Methods

ABSTRACT

A tool which employs an internal fluid during operation in a subterranean environment at elevated pressures and/or temperatures, the tool including a modular pressure compensator component which can be easily and rapidly replaced as needed. Also described is a related method of maintaining a tool which employs an internal fluid during operation in a subterranean environment at one or more pressures above atmospheric pressure, and a related method of compensating for pressure changes within a tool which employs an internal fluid during operation in a subterranean environment at super-atmospheric pressures.

TECHNICAL FIELD

The relevant technical field is the field of tools configured for deployment in environments having elevated pressures and/or temperatures, and methods of maintaining such tools.

THE INVENTION

Mechanical, electro-mechanical, hydraulic and pneumatic tools of varying complexity are frequently deployed to carry out various operations in harsh environments. Some of these tools are designed to operate effectively using a confined fluid (sometimes also referenced herein as an “internal fluid”) sealed within the tool to minimize leakage out into, or infiltration by, another fluid (sometimes also referenced herein as an “external fluid”) in or from the surrounding environment. The external fluid will typically be liquids and/or gases, usually containing hydrocarbons, from a surrounding geological formation or body of water. When the surrounding environment is under one or more pressures and/or temperatures such that the internal fluid pressure differs from the external fluid pressure from time to time, the external fluids may leak into the tool and damage component parts, and there can be a risk of explosion or implosion of the tool when the pressure differential is great. Some tools are equipped to compensate in some manner for such pressure differentials between the internal and external fluids. Operational maintenance of conventional pressure compensator systems has required significant expenditures of time and additional equipment such as hand pumps and oil reservoirs. Field failures of compensation systems and routine maintenance of compensation systems can require extensive service time by trained personnel due to the tight integration of compensation devices with the tool. Existing tool designs, even those which are equipped or configured to provide some form of pressure compensation, are replaced when the pressure compensation components become worn. Thus, a need continues to exist for a tool design capable of accommodating such pressure changes and accompanying stresses upon the tool and its components, while being easier to maintain so as to extend the tool's useful life.

This invention addresses this and other needs by providing a tool designed to compensate for pressure differentials which arise between fluids internal and external to the tool, doing so in a modular fashion so that the pressure compensation component can be easily replaced when the compensator component reaches, or approaches, the end of its useful life or is otherwise damaged. In certain aspects, the invention enables field personnel at the surface to simply swap out the pressure compensation module between tool deployments such as, e.g., downhole trips. Furthermore, the use of quick-connect-style couplings in certain aspects of the invention enable field personnel to quickly exchange the module.

Thus, in one aspect, the invention provides a tool which employs an internal fluid during operation in a subterranean environment at one or more pressures above atmospheric pressure. The tool comprises:

-   a primary tool housing which at least defines an internal fluid     volume for containing the internal fluid; -   a secondary volume-adjustable housing defining at least one     adjustable volume, the secondary housing being sized and configured     so that the adjustable volume is in fluid communication with only     the internal fluid volume of the tool during operation of the tool;     and -   a coupling sized and configured to detachably attach the secondary     volume-adjustable housing to a conduit in fluid communication with     the internal fluid volume, so that the adjustable volume is placed     in substantially sealed fluid communication with the internal fluid     volume when the secondary volume-adjustable housing is exposed to     one or more pressures of the external fluid;     wherein the tool defines a cavity that is in fluid communication     with an external fluid from the subterranean environment during     operation of the tool in the subterranean environment, so that     during operation of the tool in the subterranean environment, the     secondary volume-adjustable housing expands or contracts the     adjustable volume in response to a pressure difference between the     internal fluid and the external fluid within the cavity.

In one particular aspect of the invention, the primary tool housing forms at least one exterior surface, the cavity of the tool is defined by the primary tool housing and is accessible from the exterior surface of the primary tool housing, the secondary volume-adjustable housing is disposed within the cavity, and the coupling is sized and configured to detachably attach the secondary volume-adjustable housing to the conduit while the secondary volume-adjustable housing is disposed within the cavity. In this way, during operation of the tool in the subterranean environment, the adjustable volume is placed in substantially sealed fluid communication with the internal fluid volume while the secondary volume-adjustable housing is exposed to one or more pressures of the external fluid within the cavity. The tool in some aspects of the invention may further comprise a cover plate sized and configured to engage with the primary tool housing and cover the cavity so that an exterior surface of the cover plate and at least a portion of the exterior surface of the primary tool housing are substantially flush with one another.

In another alternative aspect of the invention, the secondary volume-adjustable housing of the tool is directly or indirectly adjacent to the cavity rather than within it, so that variations in the pressure of the pressurized external fluid within the cavity acts upon at least a portion of the secondary volume-adjustable housing to thereby influence the size of the adjustable volume in which internal fluid resides, compensating for changes in the difference in pressures between the internal and external fluids. Thus, in one aspect of the invention, the tool comprises a spring-biased piston seated within a piston cylinder, so that the cavity is defined by a face of the piston and a portion of the piston cylinder, and the secondary volume-adjustable housing is configured for detachable attachment to the primary housing, and further defines one or more passageways extending along a longitudinal axis of the secondary volume-adjustable housing and sized to receive at least one transmission line for the transmission of power and/or signals through the tool. The tool in some aspects of the invention may further comprise a mechanism for attaching the secondary and primary housings together while also mating the coupling together. For example, the tool may further comprise a threaded cylindrical sleeve disposed around a portion of the secondary housing and configured so as to provide a threaded connection of the secondary housing to a portion of the primary housing and to urge engagement of the coupling to detachably attach the secondary volume-adjustable housing to the conduit.

In another aspect, the invention provides a method of maintaining a tool which employs an internal fluid during operation in a subterranean environment at one or more pressures above atmospheric pressure. The method comprises:

placing a first secondary volume-adjustable housing within or adjacent to a cavity defined by the tool, the cavity being sized and configured to be in fluid communication with an external fluid from the subterranean environment during operation of the tool in the subterranean environment;

detachably coupling the first secondary volume-adjustable housing to a conduit so as to place at least one adjustable volume defined by the first secondary volume-adjustable housing in fluid communication with the internal fluid of the tool, and to substantially maintain a seal between the internal fluid of the tool and the external fluid when the tool in operation is exposed to the external fluid;

exposing the tool to the external fluid during subterranean operation of the tool, so that the first secondary volume-adjustable housing expands or contracts the adjustable volume in response to a pressure difference between the internal fluid and the external fluid;

recovering the tool from the subterranean environment and uncoupling the first secondary volume-adjustable housing from the conduit; and

detachably coupling to the conduit a second secondary volume-adjustable housing in replacement of the first secondary volume-adjustable housing so as to place at least one adjustable volume defined by the second secondary volume-adjustable housing in fluid communication with the internal fluid of the tool, and re-forming a seal between the internal fluid of the tool and the external fluid when the tool in operation is again exposed to the external fluid.

Still another aspect of the invention provides a method of compensating for pressure changes within a tool which employs an internal fluid during operation in a subterranean environment at one or more pressures above atmospheric pressure. The method comprises:

placing a first secondary volume-adjustable housing within or adjacent to a cavity defined by the tool, the cavity being sized and configured to be in fluid communication with an external fluid from the subterranean environment during operation of the tool in the subterranean environment;

detachably coupling the first secondary volume-adjustable housing to a conduit so as to place at least one adjustable volume defined by the first secondary volume-adjustable housing in fluid communication with the internal fluid of the tool, and to substantially maintain a seal between the internal fluid of the tool and the external fluid when the tool in operation is exposed to the external fluid;

exposing the tool to the external fluid during subterranean operation of the tool, so that the first secondary volume-adjustable housing expands or contracts the adjustable volume in response to a pressure difference between the internal fluid and the external fluid;

recovering the tool from the subterranean environment and uncoupling the first volume-adjustable housing from the conduit; and

detachably coupling a second secondary volume-adjustable housing to the conduit in replacement of the first secondary volume-adjustable housing so as to place at least one adjustable volume defined by the second secondary volume-adjustable housing in fluid communication with the internal fluid of the tool, and re-forming a seal between the internal fluid of the tool and the external fluid when the tool in operation is again exposed to the external fluid.

In particular aspects of the invention, the coupling and uncoupling is carried out using a quick connect-type valve coupling. In this way, the modular component of the tool which provides the adjustable volume necessary for internal fluid pressure compensation can be conveniently and quickly replaced with another like modular component, when and as needed.

These and still other aspects, features and advantages of the invention will now become even more apparent from the following figures, detailed description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevated view in perspective of a tool according to one aspect of the invention.

FIG. 2 is an elevated view in perspective of the tool of FIG. 1, with the cover plates and screws partially blown away.

FIG. 3 is a cross-sectional view of the tool of FIG. 1, the cross-section being cut along line 3-3 shown in FIG. 1.

FIG. 4 is a cross-sectional view of another aspect of the invention illustrating an alternative to that which is illustrated in FIG. 3.

FIG. 5 is an enlarged cross-sectional view of the device of FIG. 4, partially broken away.

FIG. 6 is a cross-sectional view similar to that of FIG. 5, illustrating another alternative aspect of the invention.

FIG. 7 is a cross-sectional view similar to that of FIG. 5, illustrating still another alternative aspect of the invention.

FIG. 8A is a cross-sectional view of another device illustrative of another aspect of the invention, showing the tool with primary and secondary housing components in a fully engaged position.

FIG. 8B is a cross-sectional view of the device of FIG. 8A, showing the tool with its primary and secondary housing components in a disengaged position.

Like numerical or letter references found in the figures refer to like parts or components illustrated amongst the several figures.

FURTHER DETAILED DESCRIPTION OF THE INVENTION

As will now be further appreciated, the devices and methods in accord with this invention provide quick connecting pressure compensation modularity to down hole tools which include an internal fluid, such as, e.g., driving units, strokers, perforators, downhole logging tools, cablehead load measuring tools, wireline tools, LWD tools, bits and other tools equipped with a sealed internal fluid, in order to facilitate rapid and selective replacement of worn or malfunctioning components in a way which is far more economical when compared to conventional tool designs and methods of repair. The particular illustrative examples which are described with particularity in this specification are not intended to limit the scope of the invention. Rather, the examples are intended as concrete illustrations of various features and advantages of the invention, and should not be construed as an exhaustive compilation of each and every possible permutation or combination of materials, components, configurations or steps one might contemplate, having the benefit of this disclosure. Similarly, in the interest of clarity, not all features of an actual implementation of a tool or related methods of use are described in this specification. It of course will be appreciated that in the development of such an actual implementation, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and economic-related constraints, which may vary from one implementation to another. Moreover, it will be appreciated that while such a development effort might be complex and time-consuming, it would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

Turning now to the accompanying figures, illustrated in FIGS. 1-2 is a portion of a tool in accordance with one aspect of the invention, the tool being configured for deployment into a subterranean well bore. The illustrated tool 10 comprises a primary housing in the form of a cylindrical, metal primary housing 12 which forms an exterior surface 14 and defines a cavity 16 which is accessible from the exterior surface 14 through cover plates 15 a and 15 b, and is sized and configured to be in fluid communication with an external fluid from the surrounding subterranean environment during operation of tool 10 in that subterranean environment. Cover plates 15 a and 15 b are sized and configured to engage with primary housing 12 and cover cavity 16 so that exterior surface 17 (on FIG. 1) of cover plates 15 a and 15 b and at least an exterior surface 14 of tool 10 are substantially flush with one another. As shown, cover plates 15 a and 15 b engage with housing 12 via screws 11, but it will be appreciated by those of skill in the art that a singular cover plate could instead be employed to perform the function of covering cavity 16, and other conventional means of detachably attaching one object to another could be used as an alternative to screws 11, as long as the cover design and attachment mechanism serves to provides protection to the pressure-compensating structures resident within cavity 16 during down hole use of tool 10. All such alternatives are within the spirit and scope of this invention.

FIG. 3 illustrates in longitudinal cross-section one alternative configuration of tool 10 of FIG. 1-2. As can be seen there, housing 12 further defines an internal fluid volume 18 for containing an internal fluid (e.g., a hydraulic fluid, or the like) residing within tool 10. Tool 10 further includes a secondary volume-adjustable housing in the form of a modular, flexible bladder 20 disposed within cavity 16 and defining at least one adjustable volume 22, bladder 20 being sized and configured so that adjustable volume 22 is in fluid communication with only internal fluid volume 18 of tool 10 during its operation. Bladder 20 is modular in that tool 10 is further equipped with a quick-connect-type valve coupling 24 facilitating a substantially sealed attachment (and substantially sealed detachment) of bladder 20 to a conduit 26 while bladder 20 is disposed within cavity 16, so that when bladder 20 is attached to conduit 26, adjustable volume 22 is placed in substantially sealed fluid communication with internal fluid volume 18 through conduit 26 while bladder 20 is exposed to one or more pressures of the external fluid present within cavity 16. Coupling 24 is comprised of a first mating component, in the form of a nipple 24 a in the example illustrated attached to conduit 26, and a second mating component, in the form of a “female” receiver 24 b in the example illustrated connected to bladder 20. In this way, detachably coupling the first secondary volume-adjustable housing (bladder 20) to conduit 26 is carried out by mating together compatible components of a quick connect-type valve coupling.

It should be further appreciated that the first secondary volume-adjustable housing is coupled to the conduit in modular fashion by mating (a) a first mating component which is connected to the conduit and (b) a second mating component which is connected to the first secondary volume-adjustable housing, so as to form a quick connect valve coupling. The second volume-adjustable housing in modular replacement of the first secondary volume-adjustable housing is coupled to the conduit by mating (c) the first mating component which is connected to the conduit and (d) a third mating component which is connected to the second secondary volume-adjustable housing, so as to form another quick connect valve coupling. During operation of tool 10 in the subterranean environment, bladder 20 expands or contracts adjustable volume 22 (thereby adjusting pressure within internal volume 18 which is in fluid communication with volume 22) in response to a pressure differential between the internal fluid and the external fluid. In this way, bladder 20 provides pressure compensation to fluid within internal volume 18 of tool 10. But, if bladder 20 becomes worn or malfunctions during the useful life of tool 10, or if replacement of bladder 20 is desired for any other reason, bladder 20 may be easily replaced in modular fashion by removing cover plates 15 a and 15 b, uncoupling bladder 20 from conduit 26 by dis-engaging the mated components of quick-connect coupling 24 while the fluid internal to the tool remains under pressure and sealed, and coupling a like bladder or other volume-adjustable housing (optionally containing fluid under pressure) and “female” receiver component to nipple 24 a and conduit 26 in the same location and manner within cavity 16. Thus, the uncoupling of the original volume-adjustable housing from the conduit is carried out without de-pressurizing the internal fluid in the tool, the secondary volume-adjustable housing contains a fluid under pressure when it is detachably coupled to the conduit, and internal fluid pressure is maintained in the tool during substitution of the second volume-adjustable housing (e.g., the new replacement bladder) for the original volume-adjustable housing. Fluid within the replacement bladder is preferably of the same type and quality as the fluid within the tool, since the replacement bladder fluid will be admixed with the tool's internal fluid after installation, and the replacement bladder fluid should be under pressure when the replacement bladder is installed via coupling 24, to avoid de-pressurizing the internal fluid of the tool during bladder replacement. The pressure of the replacement bladder fluid at the time of re-coupling to conduit 26 can vary but preferably is substantially equal to the pressure of the fluid within internal volume 18. Once bladder replacement is accomplished, plates 15 a and 15 b are then re-attached to housing 12, providing again a covered, easily replaceable, pressure compensation module flush-mounted within tool 10.

In an alternative configuration of tool 10 illustrated in FIGS. 4-5 in longitudinal cross-section, instead of employing a flexible bladder 20 as illustrated in FIG. 3, the secondary volume-adjustable housing is in the form of a modular piston housing 30 having a connecting end portion 30 a and a distal end portion 30 b, portions 30 a and 30 b being threadably mated to one another and brought into substantially sealed relation by a seal ring 31. Housing 30 houses a piston 32 biased toward portion 30 b by a spring 34 connected to portion 30 a by a spring adaptor 33 and extending between portion 30 a and piston 32. Piston 32 is placed in substantially sealed relation with an inner wall 36 of housing 30 by a seal ring 38. Substantially sealed adjustable volume 22 is thus provided within housing 30 between piston 32 and a connection end portion 30 a of housing 30. An unsealed volume 16 a within housing 30 is brought into fluid communication with cavity 16 through a fluid pathway 16 b extending through distal end portion 30 b of housing 30. During use in subterranean environments, differentials in pressure between the internal fluid in volumes 18 and 22, and the external fluid in volume 16 a will cause piston 32 to slide toward or away from distal end portion 30 b, adjusting volume 22 to compensate for such differential. In a manner similar to that for the device of FIG. 3, if housing 30 or any of its moving or expendable parts becomes worn or malfunctions during the useful life of tool 10, housing 30 may be easily replaced by removing cover plates 15 a and 15 b (shown blown away for illustrative purposes in FIG. 4), uncoupling housing 30 at quick-connect coupling 24 and coupling a like modular piston housing in the same location and manner within cavity 16. Plates 15 a and 15 b thereafter may be re-attached to housing 12, providing again a covered, easily replaceable, pressure compensation module flush-mounted within tool 10.

The internal fluid pressures for fluid within the tool and/or in the adjustable-volume housings of the invention at the surface can vary widely, but will typically be in the range of about 20 psi to about 200 psi (about 138 kPa to about 1380 kPa), although higher or lower pressures may be appropriate under a given set of circumstances for a given tool or application.

In another alternative configuration of tool 10 depicted in FIG. 6 in longitudinal cross-section, the secondary, volume-adjustable housing is in the form of bellows 40 which enclose adjustable volume 22 and are disposed within cavity 16. Likewise, FIG. 7 illustrates yet another alternative configuration illustrated in longitudinal cross-section, where the secondary, volume-adjustable housing is in the form of a flex-can 50 which encloses adjustable volume 22 and is disposed within cavity 16. In the configuration of FIG. 7, flex-can 50 comprises an assembly comprising a plurality of interconnected and alternating cylindrical segments 52 and 53 which are all aligned at their respective center points along an imaginary longitudinal axis A. An end cap 54 encloses a distal end portion 55 of the aligned plurality of cylindrical segments 52 and 53 opposing an connecting end portion 56 in substantially sealed relationship with coupling 24. Examples of a bellows or flex-can components suitable for these configurations are commercially available from, for example, Sealwise Co., Ltd. of Thasai, Muang, Nonthaburi, Thailand.

Tools of the invention can be configured to include other features to enable electrical, optical or other pathways to be made and maintained across the tool and along the string of which the tool forms a part, while still providing rapid coupling and decoupling of an internal fluid line with a pressure compensation modular component's adjustable fluid volume. FIGS. 8A and 8B illustrate an example of an aspect of the invention having one or more of such features, providing some variation in structure and/or function from the other illustrated examples. In those two figures, it may be seen that a tool 60 employing an internal fluid during operation is comprised of a cylindrical, metal primary tool housing 62 comprising portions 62 a and 62 b and forming at least one exterior surface 64, and defines an internal fluid volume 67 for containing the tool's internal fluid. Primary housing 62 further defines at least one passageway 65 extending along or parallel to a longitudinal axis A, passageway 65 sized to receive, e.g., at least one transmission line for provision of electrical or optical signals or electrical power through tool 60. Tool 60 further comprises a secondary volume-adjustable housing 66 comprising a cylindrical, metal, modular segment 68 defining electrical/optical passageway 70 containing a line leading to an electrical/optical coupling 71, and defining an internal fluid passageway 72 in fluid communication with a quick-connect coupling 24.

Housing 66 further comprises a spring 73 and a spring-biased piston 74 seated within a piston cylinder 75 formed by segment 68. A cavity 76 is thus defined by a face 74′ of piston 74 and an inner surface 75′ of cylinder 75. Segment 68 defines an adjustable volume 78, and secondary housing 66 is sized and configured so that adjustable volume 78 is in fluid communication with only internal fluid volume 67 of tool 60 through coupling 24 during operation of tool 60. Cavity 76 is sized and configured to be in fluid communication with an external fluid from the subterranean environment during operation of tool 60 in the subterranean environment, by way of two apertures 79, 79 extending from cavity 76 through cylinder 75. Secondary housing 66, via segment 68, is coupled to primary housing 62 so that electrical coupling 71 and coupling 24 mate when a cylindrical, threaded sleeve 80 is disposed around segment 68 and threadably engaged to primary housing 62 at threads 82. While quick-connect coupling 24 is fully engaged and tool 60 is in use in a pressurized environment as shown in FIG. 8A, pressurized external fluid will enter cavity 76 through apertures 79,79 and exert force on face 74′ of spring-biased piston 74 as it is biased by opposing compression spring 73 disposed around a hollow, threaded piston guide insert 84 upon which piston 74 is slidably engaged. Secondary housing 66 further comprises a cylindrical end cap 86 which is engaged with segment 68 so as to further define cavity 76 and is configured to receive an end 85 of insert 84 opposite a threaded end 83 of insert 84. End cap 86 further defines a central bore 88 for receiving electrical or optical line terminating at an electrical or optical male terminal 89. Seal rings 90 and 91 and their illustrated wiper rings R and R′ substantially seal internal fluid in adjustable volume 78 from the content (e.g., external fluid) of cavity 76. In the device illustrated, additional seal rings 92 and 93 and 94 provide further sealing at the junctions between insert 84 and segment 68 or end cap 86, as applicable. Additional seal rings 95 and 96 seal space between segment 68 and primary housing 62 when threaded sleeve 80 is rotated into an engaged position, as seen in FIG. 8A. FIG. 8B thus illustrates the same components of tool 60, but in a disengaged position.

As noted above, tool 60 of FIGS. 8A and 8B further comprises a quick-connect coupling 24 sized and configured to detachably attach secondary volume-adjustable housing segment 68 to a conduit 69, so that adjustable volume 78 is placed in substantially sealed fluid communication with internal fluid volume 67 while tool 60, and in particular secondary volume-adjustable housing 66, is exposed to one or more pressures of the external fluid. During operation of tool 60 in the subterranean environment, biased piston 74 of secondary volume-adjustable housing 66 slides on insert 84 to expand or contract the adjustable volume 78 in response to pressure differences between internal fluid in volume 78 and external fluid in cavity 76.

While specific examples of the primary and secondary volume-adjustable housing components of the invention are illustrated here with particularity, it will be appreciated that other alternative housing configurations may suffice in particular circumstances for a given set of performance requirements. For example, rather than tension/compression spring biasing, other forms of biasing in a piston configuration as illustrated can be envisioned, including, for example, leaf springs, Belleville washers, disc springs, and the like. In addition, other mechanisms for engaging housing components together in certain aspects of the invention, beyond the cylindrical threaded sleeve illustrated here, such as, e.g., screws, set screws, shear pins, and collets can be envisioned. The suitability of such alternative housing designs will be evident to those of ordinary skill in the art having the benefit of this disclosure and knowledge of the particular requirements of a given tool application.

The tool housing components, conduits, couplings, springs, pistons, cover plates and pressure compensator module assemblies may be made from the same or different materials, and such materials may include, e.g., high strength steel materials, metal alloys (e.g., INCONEL™ alloys, MONEL™ alloys or the like) or other rigid, non-elastomeric materials, and the like. Seal rings and wiper rings of certain embodiments of the invention may be made of any conventional material, with non-limiting examples of such material including metal, elastomeric, graphite, ceramic materials and the like. The bladder component in at least one aspect of the invention described herein may be made from, e.g., flexible rubber or elastomeric materials, or the like. It will be appreciated that the quick-connect type valve coupling in embodiments of the invention enables the use of the various compensation modalities interchangeably, so that the tool casing can be used and re-used with different, selected compensation modules which may be swapped out to enable optimization of the tool's compensator performance under a given set of circumstances.

Except as may be expressly otherwise indicated, the article “a” or “an” if and as used herein is not intended to limit, and should not be construed as limiting, the description or a claim to a single element to which the article refers. Rather, the article “a” or “an” if and as used herein is intended to cover one or more such elements, unless the text expressly indicates otherwise. Furthermore, aspects of the invention may comprise, consistent essentially of, or consist of the indicated elements or method steps.

This invention is susceptible to considerable variation within the spirit and scope of the appended claims. 

1. A tool which employs an internal fluid during operation in a subterranean environment at one or more pressures above atmospheric pressure, the tool comprising: a primary tool housing which at least defines an internal fluid volume for containing the internal fluid; a secondary volume-adjustable housing defining at least one adjustable volume, the secondary housing being sized and configured so that the adjustable volume is in fluid communication with only the internal fluid volume of the tool during operation of the tool; and a coupling sized and configured to detachably attach the secondary volume-adjustable housing to a conduit in fluid communication with the internal fluid volume, so that the adjustable volume is placed in substantially sealed fluid communication with the internal fluid volume when the secondary volume-adjustable housing is exposed to one or more pressures of the external fluid; wherein the tool defines a cavity that is in fluid communication with an external fluid from the subterranean environment during operation of the tool in the subterranean environment, so that during operation of the tool in the subterranean environment, the secondary volume-adjustable housing expands or contracts the adjustable volume in response to a pressure difference between the internal fluid and the external fluid within the cavity.
 2. The tool according to claim 1, wherein the coupling comprises a quick connect-type valve coupling.
 3. The tool according to claim 1, wherein the primary tool housing forms at least one exterior surface, wherein the cavity is defined by the primary tool housing and is accessible from the exterior surface of the primary tool housing, wherein the secondary volume-adjustable housing is disposed within the cavity, and wherein the coupling is sized and configured to detachably attach the secondary volume-adjustable housing to the conduit while the secondary volume-adjustable housing is disposed within the cavity, so that during operation of the tool in the subterranean environment the adjustable volume is placed in substantially sealed fluid communication with the internal fluid volume while the secondary volume-adjustable housing is exposed to one or more pressures of the external fluid within the cavity.
 4. The tool according to claim 3, wherein the coupling comprises a quick connect-type valve coupling.
 5. The tool according to claim 4, further comprising a cover plate sized and configured to engage with the primary tool housing and cover the cavity so that an exterior surface of the cover plate and at least a portion of the exterior surface of the primary tool housing are substantially flush with one another.
 6. The tool according to claim 4, wherein the secondary volume-adjustable housing comprises an assembly comprising a plurality of cylindrical segments aligned at their respective center points along an imaginary longitudinal axis and an end cap enclosing one end of the aligned plurality of cylindrical segments.
 7. The tool according to claim 4, wherein the secondary volume-adjustable housing comprises one or more bellows.
 8. The tool according to claim 4, wherein the secondary volume-adjustable housing comprises a bladder.
 9. The tool according to claim 8, further comprising a cover plate sized and configured to engage with the primary tool housing and cover the cavity so that an exterior surface of the cover plate and at least a portion of the exterior surface of the primary tool housing are substantially flush with one another.
 10. The tool according to claim 1, wherein the secondary volume-adjustable housing comprises a spring-biased piston seated within a piston cylinder, so that the cavity is defined by a face of the piston and a portion of the piston cylinder, and the secondary volume-adjustable housing is configured for detachable attachment to the primary housing, and further defines one or more passageways extending along a longitudinal axis of the secondary volume-adjustable housing and sized to receive at least one transmission line for the transmission of power and/or signals through the tool.
 11. The tool according to claim 10, further comprising a threaded cylindrical sleeve disposed around a portion of the secondary housing and configured so as to provide a threaded connection of the secondary housing to a portion of the primary housing and to urge engagement of the coupling to detachably attach the secondary volume-adjustable housing to the conduit.
 12. A method of maintaining a tool which employs an internal fluid during operation in a subterranean environment at one or more pressures above atmospheric pressure, the method comprising: placing a first secondary volume-adjustable housing within or adjacent to a cavity defined by the tool, the cavity being sized and configured to be in fluid communication with an external fluid from the subterranean environment during operation of the tool in the subterranean environment; detachably coupling the first secondary volume-adjustable housing to a conduit so as to place at least one adjustable volume defined by the first secondary volume-adjustable housing in fluid communication with the internal fluid of the tool, and to substantially maintain a seal between the internal fluid of the tool and the external fluid when the tool in operation is exposed to the external fluid; exposing the tool to the external fluid during subterranean operation of the tool, so that the first secondary volume-adjustable housing expands or contracts the adjustable volume in response to a pressure difference between the internal fluid and the external fluid; recovering the tool from the subterranean environment and uncoupling the first secondary volume-adjustable housing from the conduit; and detachably coupling to the conduit a second secondary volume-adjustable housing in replacement of the first secondary volume-adjustable housing so as to place at least one adjustable volume defined by the second secondary volume-adjustable housing in fluid communication with the internal fluid of the tool, and re-forming a seal between the internal fluid of the tool and the external fluid when the tool in operation is again exposed to the external fluid.
 13. The method according to claim 12, wherein the step of detachably coupling the first secondary volume-adjustable housing to the conduit is carried out by mating together compatible components of a quick connect-type valve coupling.
 14. The method according to claim 12, wherein the first secondary volume-adjustable housing is placed within the cavity, the cavity being both defined by a primary housing of the tool and accessible from an exterior surface of the primary housing, the method further comprising covering the cavity with a cover plate when the second volume-adjustable housing is coupled to the conduit, so that an exterior surface of the cover plate and at least a portion of the exterior surface of the tool are substantially flush with one another.
 15. The method according to claim 14, wherein each of the steps of detachably coupling the first secondary volume-adjustable housing to the conduit and detachably coupling the second secondary volume-adjustable housing to the conduit is carried out by mating together compatible components of a quick connect-type valve coupling.
 16. The method according to claim 12, wherein the uncoupling of the first secondary volume-adjustable housing from the conduit is carried out without de-pressurizing the internal fluid in the tool, the second secondary volume-adjustable housing contains a fluid under pressure when it is detachably coupled to the conduit, and the method further comprises maintaining internal fluid pressure in the tool during substitution of the second secondary volume-adjustable housing for the first secondary volume-adjustable housing.
 17. A method of compensating for pressure changes within a tool which employs an internal fluid during operation in a subterranean environment at one or more pressures above atmospheric pressure, the method comprising: placing a first secondary volume-adjustable housing within or adjacent to a cavity defined by the tool, the cavity being sized and configured to be in fluid communication with an external fluid from the subterranean environment during operation of the tool in the subterranean environment; detachably coupling the first secondary volume-adjustable housing to a conduit so as to place at least one adjustable volume defined by the first secondary volume-adjustable housing in fluid communication with the internal fluid of the tool, and to substantially maintain a seal between the internal fluid of the tool and the external fluid when the tool in operation is exposed to the external fluid; exposing the tool to the external fluid during subterranean operation of the tool, so that the first secondary volume-adjustable housing expands or contracts the adjustable volume in response to a pressure difference between the internal fluid and the external fluid; recovering the tool from the subterranean environment and uncoupling the first volume-adjustable housing from the conduit; and detachably coupling a second secondary volume-adjustable housing to the conduit in replacement of the first secondary volume-adjustable housing so as to place at least one adjustable volume defined by the second secondary volume-adjustable housing in fluid communication with the internal fluid of the tool, and re-forming a seal between the internal fluid of the tool and the external fluid when the tool in operation is again exposed to the external fluid.
 18. The method according to claim 17, wherein the first secondary volume-adjustable housing is coupled to the conduit by mating (a) a first mating component which is connected to the conduit and (b) a second mating component which is connected to the first secondary volume-adjustable housing, so as to form a quick connect valve coupling, and wherein the second volume-adjustable housing is coupled to the conduit by mating (c) the first mating component which is connected to the conduit and (d) a third mating component which is connected to the second secondary volume-adjustable housing, so as to form another quick connect valve coupling.
 19. The method according to claim 18, wherein the uncoupling of the first volume-adjustable housing from the conduit is carried out without de-pressurizing the internal fluid in the tool, the second volume-adjustable housing contains a fluid under pressure when it is detachably coupled to the conduit, and the method further comprises maintaining internal fluid pressure in the tool during substitution of the second volume-adjustable housing for the first volume-adjustable housing.
 20. The method according to claim 17, wherein the uncoupling of the first volume-adjustable housing from the conduit is carried out without de-pressurizing the internal fluid in the tool, the second volume-adjustable housing contains a fluid under pressure when it is detachably coupled to the conduit, and the method further comprises maintaining internal fluid pressure in the tool during substitution of the second volume-adjustable housing for the first volume-adjustable housing. 